Electric switch



1934- c. H. FLURSCHEiM 1,970,421

ELECTRIC SWITCH Filed Nov. 2, 1952 1-. Inventor:

I Cedric H.F |ur"scheim, by .j t/

His Attorney.

Patented Aug. 14, 1934 UNITED STATES PATENTj: OFFICEApplicationflovember 2, 1932, Serial No. 640,745

In Great Britain November 24, 1931 5 Claims.

My invention relates to electric switches or circuit breakers of theheavy duty type.

In heavy duty circuit breakers having large current carrying capacitythe resistance at the coacting contact surfaces may assume considerableimportance since excessive heating results if the contact resistance isnot within a certain value. It has been found that the contactresistance may be greatly reduced by increasing the contact pressure andto this end high pressure line or point contact between the coactingcontact members has been proposed.

A principal object of my invention is the provision of an improved heavyduty circuit breaker of the aforesaid type wherein the coacting contactsare forced into high pressure engagement in the closed circuit position.

My invention will be more. fully set forth in the following descriptionreferring to the accompanying drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 illustrates my invention as applied, byway of example, to a single-phase, double-break circuit breaker; Fig. 2is an end elevation, partly in section, of the aforesaid contactassembly; Fig. 3 is a detailed perspective view of the assembly with onestationary contact removed, and Figs. 4 and 5 show in plan andelevation, respectively, one of the mechanical elements employed in theassembly.

In accordance with a preferred form of my invention, the switch contactsare arranged so that during the initial part of the relative circuitclosing movement of the contacts a switch blade or bridging member isinserted within coacting switch jaws. During the latter part of therelative movement of the contacts the switch blade is caused to expandlaterally, or alternatively, the switch jaws are caused to contract inorder to produce high contact pressure at the coacting contact surfaces.The expansion of the switch blade or the contraction of the switch jaws,as the case may be, may be initiated by engagement of one contact with astop carried on the other contact or on the supporting frame structuretherefor.

In practising the invention, the switch may be provided with one or moremechanical purchase devices, such as toggle mechanisms, lever systems orcams, which are operated by the switch actuating member.- during thefinal part of its operating movement for bringing the contacts intoengagement, to apply force for expanding the switch blade or contractingthe switch jaws,

as the case may be.

Referring more particularly to Fig. 1 of the drawing, the single-phase,double-break oil circuit breaker illustrated comprises two stationarycontacts 1 and 1', each of said contacts being provided with rigiddepending jaws. The coacting bridging contact assembly 2 is providedwith operating means as draw-rods 3 of insulating material which aresecured to projections 4' on a main cross-frame 4. The aforesaidrelatively movable contact structure is suitably mounted within theusual oil-containing tank (not shown) and the operating rods 3 areactuated in any suitable manner to cause vertical reciprocal movement ofthe bridging structure 2.

The cross-frame 4 has on each side U-shaped projections 12 providinglimiting stops 5, 6 and 7 for the upward, downward and inward movements,respectively, relatively to the cross-frame 4 of a pair of currentcarrying straps or bars 8. A strap 8 is mounted on each side of thecrossframe and is resiliently constrained by tension springs 9 in anupward and inward direction towards the stops 5 and 12 respectively.

For the purpose of forcing the conducting straps 8 into high pressurecontact engagement with the coacting stationary contacts, pairs oftoggles and 10 are provided at each end of the main cross-frame 4. Thesetoggles are pivoted at their outer ends in the current carrying straps 8and at their inner ends in the cross-frame 4 so that they are free torotate about horizontal axes when the cross frame is moved vertically.The toggles as shown in-detail in Figs. 4 and 5 are constructed of twostrips 13 and 14 secured together as by pins 16 at their ends with shortadjustable spacing pieces between their ends. The strips 13 and 14 arethus free to deflect slightly at the center when the toggle is undercompression, thereby providing a certain amount of resiliency withineach toggle member. The length of the toggles may be adjusted to givethe desired compression and contact pressure on the contacts by alteringthe adjustable spacing pieces 15.

For the purpose of positioning the toggle members spherical headed pivotpins 17 and 18 project outwardly from the center of each of the togglestrips 13 and 14 respectively. The pins 18 cooperate with the currentcarrying straps 8 and, as shown in Fig. 2, hear at the center of thesestraps in recesses formed in hardened thrust plates 11 attached to thestraps. The

opposite pivot pins 17 of each toggle pass through holes 19 in the maincross-frame 4 and abut each other, the holes 19 allowing a small amountof horizontal movement of the pins to provide for self-alignment of thecontacts and being substantially opposite the center line of the currentcarrying straps 8 when in the closed position of the circuit breaker.

Arcing contacts 20 of conventional design are secured to the stationarycontacts, and coacting removable arcing contacts 21 are provided at theends of the main conducting cross-frame 4.

In operation when the circuit breaker is in the open circuit position,the moving contact assembly 2 is clear of and beneath the fixed contacts1 and 1, and the conducting straps 8 are held against the top and innerstops 5 and 7 respectively of the U-shaped projections 12 by the springs9. These springs are of sufficient strength to maintain the straps 8 inthis position while the moving contact 2 is being accelerated during theclosing operation. When the straps 8 are against these stops 5 and 7 theoverall width of the moving bridging contact is less than the spacebetween the rigid jaws of the fixed contacts 1 and 1, and the toggles 10and 10' are tilted downwardly at their abutting ends relatively to eachother.

The operating or draw-rods 3 therefore meet with no mechanicalresistance during the closing operation until the top faces of thestraps 8 meet the fixed contacts 1 and 1 on the face between the jawsand are arrested thereby. The main cross-frame 4 continues to rise withthe pulling of the draw-rods 3 and the toggles 10 and 10 becomestraightened out relatively to one another as shown in Fig. 2, at thesame time forcing the straps 8 against the jaws until in the fullyclosed position the toggles 10 and 10 are in the same straight line orhave passed very slightly beyond it.

In the closed circuit position, in the event of a heavy fault or shortcircuit occurring, the repelling force on the current carrying straps 8would be resisted by the frictional force between v the faces of thesestraps and the rigid jaws of the fiixed contacts 1 and 1, and if this isinsufficient, the lower projecting stops 6 of the main cross-frame 4serve as stops to limit the slip that can occur.

When the breaker is tripped in any well known manner causing lowering ofthe draw-rods 3, the main cross-frame 4 moves downwards, releasing thetoggles 10 and 10'. The current carrying straps 8 now released frompressure are carried downwards as soon as they are met by the upperstops 5 of the U-shaped projections 12 on the main cross-frame 4, themechanism being then in the correct position for reclosure.

It will, therefore, be apparent that the coacting contact surfaces of acircuit breaker embodying my invention are positively forced into highpressure engagement in accordance with the switch closing operation andare automatically released in accordance with the initial circuitopening movement.

It should be understood that my invention is not limited to specificdetails of construction and arrangement thereof herein illustrated, andthat changes and modflcations may occur to one skilled in the artwithout departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStatets is:

1. An electric circuit breaker comprising relatively movable contactsincluding a bridging contact having a pair of blades each arranged toengage and interconnect a pair of coacting contacts, operating meanssupporting said bridging contact, and means including toggle membersoperatively connected to said operating means and opposite ends of saidblades for expanding and forcing the, same into high pressure contactwith said coacting contacts, said toggle members actuated in accordancewith the final circuit closing operation of said breaker.

2. An electric circuit breaker comprising relatively movable contactsincluding a contact having a supporting frame and a pair of relativelymovable blades carried thereby at opposite sides of said frame andparallel therewith arranged to engage and interconnect opposing faces ofa coacting contact, and means including toggle members interconnectingsaid frame and blades for forcing said blades into high pressure contactwith said opposing contact faces respectively, engagement of said bladesand coacting contact during the final circuit closing operation of saidbreaker causing straightening and actuation of said toggle members.

3. An electric circuit breaker comprising a stationary contact havingspaced depending jaws and a coacting movable contact including Psupporting frame and a pair of blades resiliently mounted thereon eacharranged to engage and interconnect the inner opposing faces of saidstationary contact jaws, and toggle members interconnecting saidsupporting frame and blades outwardly and .into high pressure contactwith said jaws respectively, said blades arranged to engage saidstationary contact during the final part of the circuit closingoperation for causing actuation of said toggle members.

4. An electric circuit breaker comprising a pair of stationary contacts,each having spaced depending jaws, and a movable bridging membercoacting therewith including a supporting frame and operating meansconnected thereto, a pair of blades resiliently mounted for limitedmovement on opposite sides of said frame, and toggle membersinterconnecting said frame and blades, each of said blades arranged toengage and interconnect said stationary contacts in advance of saidframe so that the final circuit closing movement of said frame iseffective to straighten said toggle members causing said blades to beforced against the opposing Jaws of said stationary contactsrespectively.

5. An electric circuit breaker comprising relatively movable contactsincluding a contact having a supporting frame and a pair of bladesarranged to engage a coacting contact, and means including togglemembers operatively connected to said blades and frame for forcing saidblades into high pressure engagement with said 00- acting contact, eachof said toggle members comprising a pair of resilient strips arranged inparallel spaced relation, spacing members joining the opposite ends ofsaid strips, and a pin connected to each strip intermediate its length,each of said pins operatively connected to said frame and a bladerespectively.

CEDRIC H. FL.

CERTIFICATE or CORRECTIQN. 3

Patent No. 1,970,421, August 3 CEDRIC H. FLURSCHEIM.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,line 113, claim 3, after "blades" insert for forcing said blades; andthat the said Letters Patent should be read with this correction thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 18th day of September, A. D. 1934.

Lesl ie Frazer (Seal) Acting Commissioner of Patents.

